jcn59,
I had gone thru similar situations with my 218 Bee, 6.5" bbl. revolver. The lowest bullet grains that I've used so far is 45gr Hornet bullet (.224). One of the factory rounds I recently purchased, are the HSM (orange color box) 218 Bee, 50 gr bullet. The velocities I've got with that is 1845 fps. I disassembled one round and the powder weigh was 14.4 gr of a powder similar in look as the H110 but with a darker black color. I am not familiar with the AA1680 powder so I could not say that's what it was. The cartridges were also cleared from the cylinder without problems. This leads me to believe that the winchester brass is somewhat weak. Granted that I had been reloading them way too many times. I only discard them when the break. I would also like to reach the 2000 fps mark some day and I think the answer is in the cartridge strengh and a hard rifle primer. I am working up some loads with H110. I started with 45gr Rem, 9.0 gr H110, and WSP pistol primers. Seems a little hot with the WSP but mild with the rifle magtech small rifle primer (MSR). I love this revolver. It is very accurate with some of the loads I have. It's like having a .22 Mag rifle at hand but in a short package.
Camba